Legend:

The Shuttle Radar Topography Mission mapped global elevations at a 3 arc second (90m posting) resolution between 60N and 56S. This is relatively coarse for DEM usage but is sufficient in some cases. To create a DEM from this data:

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1. Obtain data from SRTM ([http://srtm.usgs.gov/ http://srtm.usgs.gov/]). This is most easily done via their [http://seamless.usgs.gov/ Seamless server] - click on "View and Download international data", then from the icons on the left select "Define download area by coordinates (icon looks like "X Y" above a ruler). A dialog will be displayed asking for the limits of the area you want to download. Enter these and click "Add Area". Another dialog will be displayed, probably saying that there are no available products in the area indicated (unless that area was in North America). Click on "Modify Data Request", and on the resulting page deselect any selected options and select "SRTM 3 arc sec - Shuttle Radar Topography Mission [Finished]" (bottom option at time of writing). Then click "Save changes and return to summary", and once the summary is displayed click on Download and save the resulting zip file somewhere. If it still says no products are available, check that your area is not over the sea or too far north or south, and that you have selected the correct product (only the SRTM 3 second data is available for sites outside North America).

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1. Obtain data from SRTM ([http://srtm.usgs.gov/ http://srtm.usgs.gov/]). This is most easily done via their [http://earthexplorer.usgs.gov Earth Explorer] - expand the "Digital Elevation" link on the left and tick the box labelled "SRTM". Enter bounding co-ordinates for the area you want data for, clicking the green "+" icon after each one. Note that this currently seems not to always work correctly for locations in DMS format (at least in Firefox), you may need to switch to decimal degrees (which work fine). Click on the "Search" button in the bottom-right, and you should be presented with a list of items matching your search (there should be only one thing in it). Click on the "SRTM" link (you may need to enable pop-ups if you've got them blocked), and you will be presented with a list of matching SRTM tiles and download links - download the data you want to use. Note that only SRTM 3-arc-second resolution data is available for sites outside North America.

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2. Unzip the downloaded zip file and descend into the directory structure to find the file w001001.adf - this holds the actual data, though you can't move it without the rest of the directory structure.